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H5N1 H9N2 Bird Flu Reassortant Identified In Israel

Recombinomics Commentary

July 26, 2006

The H5N1 bird flu NS sequence  from a turkey in Israel, A/turkey/Israel/345/06(H5N1) has been released.  Although the other seven gene segments have not been released, the H5N1 sequence is clearly the Qinghai strain.  It has several Qinghai specific polymorphisms as well as a 15 BP deletion that is one of the markers that defines in the Z genotype and is linked to increased virulence.

The sequence has three informative markers, C137T, C320T, and A584G which are also in A/turkey/Turkey/1/05(H5N1).  The latter two markers are also in a number of Qinghai isolates, including the four human isolates from Turkey as well as 2005 isolates from Russia and Mongolia.

However, in addition to the one H5N1 sequence, 22 H9N2 NS sequences were also released.  The collection dates ranged from 2000 to 2006.  One of these 2006 sequences, A/turkey/Israel/446/06(H9N2), was an exact match of the H5N1 Israeli turkey sequence, indicating the H9N2 isolate was a reassortant formed via a dual infection between H5N1 and H9N2.

Such a dual infection had been predicted in October 22, 2005 and a warning that such a dual infection could lead to the acquisition of HA S227N because H9N2 in the Middle East had appropriate donor sequences.  In early 2006, S227N was reported in two of the four human H5N1 sequences from Turkey, including the isolate from the index case A/Turkey/12/06(H5N1), who was linked to a very large cluster involving multiple families of cousins..

The H5N1/H9N2 reassortant in Israel is cause for concern and human infections may be under-reported.  Israel had reported a suspect case with confirmed antibodies to H5N1, but re-confirmation attempts failed.  The sharing of H5N1 polymorphisms with the first Qinghai H5N1 isolated in the area (western Turkey in 2005), suggest H5N1 had been in Israel long before its first reported case in poultry in 2006.

The sequence of the other 7 gene segments from both the H5N1 and other 2006 H9N2 isolates would be of interest because both reassortment and recombination between H5N1 and H9N2 may have been widespread in the Middle East because of endemic H9N2 and migration of Qinghai H5N1 into the region.

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